1. Field of the Invention
This invention relates to a type of humeral prosthesis that is provided with a rod to be anchored in the humeral canal of a patient, a metaphyseal element that extends upwards from said rod and towards the inside, this metaphyseal element being fitted, at an area of connection, to a flange against which rests an approximately hemispheric calotte or cap suitable to interact with the shoulder socket. The mentioned area of connection is arranged approximately along a median line of the flange.
2. History of the Related Art
When the upper extremity of the humerus is fractured, the humerus generally breaks into several pieces, in particular the shaft, the humeral tuberosities and, lastly, the head of the humerus that interacts with the shoulder socket.
When such a fracture is set, only the head of the humerus must be replaced by an approximately hemispheric cap, while the other fractured pieces may be set around a prosthesis.
Well known in the art are prosthesis of this type which, as a rule, comprise a rod, or shaft portion, that is inserted in the humeral canal of the shaft of the bone. This rod is extended by a metaphyseal element that is bent upwards and towards the inside of a prosthesis worn by a standing patient, around which prosthesis are brought together the tuberosities constituting the metaphysis of the bone with the intention of setting them. The metaphyseal element of the prothesis is joined to a flange of the seat of a cap replacing the head of the humerus.
This type of protheses, such as, for example, those of NEER, present however certain disadvantages. In fact, they are made out of one only block which renders it necessary to have a large number of implants to meet the anatomic requirements of the different patients. Furthermore, these prosthesis have only one size of rod and of cap, and the latter cannot be offset as proven necessary in some cases. Moreover, the space of the upper portion of the prosthesis does not allow, in the case of serious fractures of the upper portion of the humerus, a satisfactory setting between the osseous fragments.
Furthermore, from French Patent A-2 689 758 is known a humeral prosthesis that comprises in its metaphyseal element a reinsertion flange. This flange is provided with perforations through which pass threads that ensure the anchoring of the bone to the prosthesis. However, the perforations of very slight diameter do not allow for the osseous fragments to come closer together. Thus, the mutual uniting of these fragments proves to be insufficient which, of course, is detrimental to the physical integrity of the patient.